Method of manufacturing a pinch in a quartz tube

ABSTRACT

A method of providing a pinch seal of restricted dimensions in a quartz glass tube in which two pressure plates act between two parallel plates on a softened part of the tube to form the pinch. The method permits removing of the pressure plates only some time after the parallel plates limiting the narrow parts of the pinch have been removed and the pinch has cooled. This results in an appropriate shaped pinch seal and a more exact placement of the pinch relative to the center line of a resultant lamp.

United States Patent Schenkels METHOD OF MANUFACTURING A PINCH IN A QUARTZ TUBE [75] Inventor: Ferdinand Jose Maria Schenkels,

Emmasingel, Eindhoven, Netherlands [73] Assignee: U. S. Philips Corporation, New

York, NY.

[22] Filed: Feb. 21, 1973 [2]] Appl. No.: 334,404

Related US. Application Data [63] Continuation of Ser. No. 126,424, Mar. 22, i971,

abandoned.

[52] US. Cl 65/108, 65/138, 65/295 [51] Int. Cl C03b 23/16 [58] Field of Search...65/39, 59, 102, 108, 138-140,

[56] References Cited UNITED STATES PATENTS 1,853,911 4/1932 McCabe 65/138 Apr. 9, 1974 2,109,544 3/1938 Marshall 65/138 3,548,245 l2/l970 Biscoff 65/139 X 3,407,054 lO/l968 Ose et al 65/l39 X Primary ExaminerRobert 1... Lindsay, Jr. Attorney, Agent, or FirmFrank R. Trifari [57] ABSTRACT A method of providing a pinch seal of restricted dimensions in a quartz glass tube in which two pressure plates act between two parallel plates on a softened part of the tube to form the pinch. The method permits removing of the pressure plates only some time after the parallel plates limiting the narrow parts of the pinch have been removed and the pinch has cooled. This results in an appropriate shaped pinch seal and a more exact placement of the pinch relative to the center line of a resultant lamp.

1 Claim, 4 Drawing Figures WWW 9.914 $802,859

Will/a Fig.4

INVENTOR.

FERDINAND J. M. SCHENKELS AGENT METHOD OF MANUFACTURING A PINCH IN A QUARTZ TUBE This is a continuation of application Ser. No. 614 41.iUQQcMaLZZLlQZIzc swa andpas The invention relates to a method of manufacturing a pinch within narrow size limits in a quartz glass tube, as well as to a pinch manufactured by the method.

It is a known from practice to manufacture such a pinch in such manner that the tube in which the pinch is to be made is placed, after heating, between two flat plates of a fork-shaped member which may be bevelled at the ends, of which member the plates form the teeth of the fork, between which plates a first pressure plate the pressure surface of which extends at right angles to the inner surfaces of the fork plates, and a second pressure plate the pressure surface of which extends parallel to the pressure surface of the first plate and which preferably has the same dimensions as the first pressure plate are forced towards each other in order to pinch the tube. By moving the two pressure plates in the fork, a pinch can be obtained the width of which does not exceed the diameter of the tube, as is usually required.

A drawback of the method described is, however, that when the pressure plates are removed, the pinch is jambed in the fork. This results in an oblique position of the pinch relative to the tube, as a result of which the pinch is no longer located exactly in the center line of the tube.

The method according to the invention produces a pinch which has the same width as the tube and the center line of which pinch coincides exactly with the center line of the tube. This method is characterized in that during the manufacture of the pinch as described above, immediately after the formation of the pinch by a relative movement of the two pressure plates towards each other, a relative movement is given to the plates of the fork-shaped member relative to the two pressure plates, which in themselves maintain their position relative to each other, by which movement the squeezed pinch is released from the plates of the fork-shaped member, the two pressure plates maintaining their position relative to each other until the pinch is sufficiently cooled.

The invention also comprises a tube of quartz glass provided with a pinch and manufactured by the abovedescribed method.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying diagrammatic drawing, which shows an embodiment of the method according to the invention, and in which:

FIG. 1 is a plan view of a fork-shaped member having two pressure plates and a tube of quartz glass,

FIG. 2 shows the same plan view as figure I but not with displaced pressure plates and the tube squeezed,

FIG. 3 shows again the same plan view but this time with displaced pressure plates, the squeezed tube (the compressed pinch) being situated outside the forkshaped member, and

FIG. 4 is a side elevation of the manufactured pinch.

Referring now to the figures, reference numeral 1 denotes a quartz glass tube in which a pinch as is shown in FIG. 4 is to be formed. The'width of said pinch is to be equal to the diameter of the tube, and the center line of the pinch should coincide with the center line of the tube.

A fork-shaped member 2 comprises two parallel plates 3 which form the teeth of the fork and the ends 4 of which-are bevelled on the inside. A hollow shaft 5 is secured to the fork-shaped member 2. Slidable in the said shaft 5 is a shaft 6 comprising at one end a pressure plate 7. Opposite to said pressure plate 7 is a second pressure plate 8 having a shaft 9 at one end. The two pressure plates extend parallel to each other and their surfaces facing each other extend at right angles to the insides of the plates 3.

When a pinch is to be made in the tube I, said tube is first heated locally until the quartz glass softens. The tube is then arranged between the plate 3 (FIG. 1), until the tube engages the plate 7. The shaft 9 comprising the plate 8 is then moved to the left, shaft 6 with plate 7 being held stationary. If desirable, the shaft 5 with the fork 2 may be moved slightly to the right. As a result of these movements a pinch I0 is formed the width of which is equal to the diameter of the tube 1. When the pinch thus formed is allowed to cool in the position shown in FIG. 2, it is found that after sufficient cooling, the pinch is jambed more or less in the fork which, upon removal, results in an inclined position of the pinch relative to the tube. According to the method of the invention, however, the shaft 5 with the fork 2 is moved to the left after the formation of the pinch and slight cooling, if desirable, so that the position shown in FIG. 3 is obtained. The pressure plates 7 and 8 remain pressed together until the cooling of the formed pinch has proceeded sufficiently, after which they are also separated.

It has been found that a fine pinch extending according to the center line of the tube is obtained by means of the method described, the width of said pinch being equal to the diameter of the tube. Of course it is not necessary to displace the shaft 5 with the fork 2. It is also possible, after the formation of the pinch, to move the shafts 6 and 9 having the pressure plates 7 and 8 to the right, it being ensured, however, that the plates 7 and 8 do not change their positions relative to each other and to the formed pinch 10.

The plates 3 may also be made so as to be .pivotable relative to the base plate of the fork 2 so that the forkshaped member is opened instead of sliding away relative to the pinch. It is alternatively possible that said plates in themselves are slidable.

It is of course also possible to manufacture in the manner described a pinch the width of which is slightly larger or smaller than the diameter of the tube.

The bevel 4 of the plates 3'is not necessary either but is recommendable indeed since it facilitates the insertion of the tube 1.

What is claimed is:

l. A method of manufacturing a pinch within narrow size limits in a quartz glass tube comprising the steps of:

heating the quartz glass tube;

placing the tube, after heating, between two flat plates of a fork-shaped member, the plates of the member forming the teeth of the fork, and between two pressure plates, a first of said plates having a pressure surface extending at right angles to the inner surface of the fork plates and the second of said plates having a pressure surface extending parallel to the pressure surface of the first plate, the

to the two pressure plates after formation of the pinch seal, prior to substantial cooling of the seal, the two pressure plates maintaining their relative position during movement of the fork plates, thereby releasing the squeezed pinch from the plates of the fork-shaped member;

and maintaining the relative position of the pressure plates until the pinch is sufficiently cooled.

UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent No. 5,802,859 Dated April 9, 197

Inventor(s) FERDINAND JOSE MARIA SCHENKELS It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 8, before "known" delete "a" sighed and sealed this 3rd day of December 1974,

C(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents vUSCOMM'DC 60376-P69 FORM eo-aoso (10-69) U.S. GOIIERNNENT PRINT NG OFHCE: 869-793 0 

1. A method of manufacturing a pinch within narrow size limits in a quartz glass tube comprising the steps of: heating the quartz glass tube; placing the tube, after heating, between two flat plates of a fork-shaped member, the plates of the member forming the teeth of the fork, and between two pressure plates, a first of said plates having a pressure surface extending at right angles to the inner surface of the fork plates and the second of said plates having a pressure surface extending parallel to the pressure surface of the first plate, the dimensions of the two pressure plates being approximately the same; forcing the two pressure plates relatively towards each other between the flat plates of the fork-shaped member, at least one of the pressure plates being moved relative to the fork-shaped member and forcing the two pressure plates against the walls of the tube to form a pinch seal; moving the plates of the fork-shaped member relative to the two pressure plates after formation of the pinch seal, prior to substantial cooling of the seal, the two pressure plates maintaining their relative position during movement of the fork plates, thereby releasing the squeezed pinch from the plates of the fork-shaped member; and maintaining the relative position of the pressure plates until the pinch is sufficiently cooled. 